1. Field of the Invention
The invention relates to an apparatus for synthesizing additional images that are stored to document images.
2. Description of Related Art
Coin-operated copying machines have become quite popular in convenience stores and other similar stores these days. Unspecified users operate these machines. Therefore, it is possible to achieve a substantial advertisement effect if additional images such as advertisement images can be added to the intended document images produced by scanning documents when the users make copies using these machines.
Therefore, a technology has been proposed to print document images with added images.
For example, the Japanese Unexamined Patent Publication No. 8-256256 discloses a technology for adding advertisement images to vacant areas of the document image. The disclosed technology provides the following process. A vacant area is detected from the document image obtained by the copying machine as it scans the document. The information concerning the detected vacant area is transmitted to the server via a network. An advertisement image that is suitable for the detected vacant area is selected from the advertisement images stored in the server. The selected image is transmitted to the image forming device. As the advertisement image is added to the vacant area, both the document image and the advertisement image are printed.
The Japanese Unexamined Patent Publication No. 6-268840 displays another technology for synthesizing the two images. According to this technology, the density of the image stored in the memory is compared with the density of the document image pixel by pixel. If the density data of the document image turns out to be higher than the prescribed value, the document image data is selected, while if it is lower, the stored image is selected. Therefore, when the stored image is synthesized with the document image according to the technology, the synthesis causes one image to appear as if it is watermarked against the other image.
Furthermore, the Japanese Unexamined Patent Publication No. 9-69935 discloses a technology for adjusting the density of at least one of the images so that it is easier to differentiate the images when two images are synthesized.
However, the copying machine disclosed by the above-mentioned Publication of Unexamined Patent Application No. 8-256256 has a shortcoming that the advertisement effect is small when the vacant area is small as only a relatively small advertisement image can be printed because the advertisement image is printed only in the vacant area of the document image. Also, it does not allow to print any advertisement image if there is no vacant space in the document image.
When the image synthesis technologies disclosed by the above-mentioned Japanese Unexamined Patent Publication No. 6-268840 and No. 9-69935 are applied to the synthesis of the advertisement image on the document image, the advertisement image appears as if it is watermarked or appears weak, so that the advertisements are difficult to see. When the document image happens to be a photograph image or a graphic image, the advertisement image that appears like a watermark or printed weakly over the document image makes it difficult to see the document image. Thus, a user who is concerned about making the document difficult to see may not wish to synthesize the advertisement image. On the other hand, the advertiser may not like to print the advertisement like a watermarked or weak image as it reduces the advertisement effect.